THE PLASMA 85 



varies normally from 1-8 to 0-85 per cent. In the pregnant animal 

 the fat content of the plasma is much increased. 



The lipoids lecithin and cholesterin are also present in the plasma, 

 and probably play a consideiable part in the protective mechanisms 

 of the body, as well as furnishing a supply of these bodies to the other 

 tissues. 



Carbohydrate. Dextrose is normally present ; the percentage 

 found varies from 0-06 to 0-1. If the content is raised above the latter 

 figure, the excess is excreted in the urine. It is a question whether 

 the dextrose is free in solution or loosely combined with the proteins ; 

 a small amount of it is combined with lecithin to form a substance 

 known as jecorin. The presence of glycuronic acid has been demon- 

 strated in the serum. It is usually combined as compound glycuron- 

 ates. It has been recently shown that the red corpuscles contain 

 sugar. 



The salts obtained from plasma form 1 to 2 per cent, of its weight, 

 and are chiefly sodium chloride, with traces of calcium, potassium, 

 and magnesium chloride and phosphate. 



The straw-yellow colouring matter of the plasma can be extracted 

 with amyl aliohol, and is called lipochrome. 



The gases of the plasma will be dealt with later. 



The plasma contains various antienzymes, immune bodies, com- 

 plement, etc., the presence of which is detected by biological tests. 



The chief products of katabolism of the various foodstuffs, presence 

 of which has been demonstrated in the plasma, are urea (0-02 to 

 0-1 per cent.), uric acid, creatin, creatinin, and traces of ammonia. 

 While it is questioned whether amino-acids are normal constituents 

 of plasma, they are undoubtedly present when any organ or tissue is 

 digesting itself (autolysis), as in phosphorus poisoning, acute yellow 

 atrophy of the liver, etc. They then make their appearance in the 

 urine. 



The plasma under diverse conditions is found to have a most 

 striking consistency in composition. Thus, after the intravenous 

 injection of water or salt solution the blood is rapidly brought to 

 the normal composition. The tissues give or take from the blood, 

 the glands secrete and kidneys excrete for this purpose. Even during 

 starvation its composition is maintained. 



